1. Field of Invention
The present invention relates to a power supply device useable in an electronic apparatus, such as a facsimile apparatus, for example. In particular, the invention relates to a power supply device by which heat produced from a regulator producing a stable DC voltage can be efficiently restrained.
2. Description of Related Art
Conventionally, in various electronic apparatuses, a power supply device is provided in which a primary side of a transformer is connected to a AC power source and a desirable DC voltage is produced at a secondary side of the transformer. With such a conventional power supply device, a preferable DC voltage is obtained by converting power into heat. Therefore, the problem arises that the power supply device heats up and energy consumption becomes large. Thus, the conventional power supply device is not preferable from an energy conservation point of view.
The present invention provides a power supply device and method useable, for example, in a facsimile apparatus or other electronic apparatus. The power supply device according to one embodiment of the invention includes a transformer with a primary side connected to an AC power source and a secondary side which produces a DC voltage. The power supply device further includes a first DC voltage producing part which produces a stable first DC voltage based on a winding ratio between a primary coil at the primary side and a secondary coil at the secondary side.
A second DC voltage producing part is provided which includes a regulator that produces a stable second DC voltage from a non-stable DC voltage changing according to a load current loaded to the first DC voltage producing part. The power supply device further includes a reducing means for reducing a load current loaded to the second DC voltage producing part when the non-stable DC voltage increase.
According to the above power supply device, when the non-stable DC voltage increases the reducing means reduces the load current loaded to the second DC voltage producing part. Thereby, even if the non-stable DC voltage increases corresponding to an increase of the load current loaded to the first DC voltage producing part, the load current loaded to the second DC voltage producing part can be reduced by the reducing means. Thus, the DC current value loaded to the regulator is reduced, as a result, energy quantity emitted from the regulator can be reduced. Further, heating of the regulator can be efficiently restrained and energy saving can be realized by reducing useless energy consumption.
When the power supply device is used in a facsimile apparatus, the facsimile apparatus having a copy function which makes use of the first DC voltage produced in the first DC voltage producing part, the reducing means may reduce the load current loaded to the second DC voltage producing part when the copy function is conducted. Further, if the above power supply device is used with a multi-function facsimile apparatus having a facsimile function, a scanner function, a printer function, a copy function, and the like, even if the load current loaded to the first DC voltage producing part increases when, for example, the copy function, in which both the scanner function and the printer function are executed at the same time, is conducted, the load current loaded to the first DC voltage producing part can be reduced by the reducing means. Thereby, the DC current value loaded to the regulator is reduced and the amount of energy emitted from the regulator can be reduced. Additionally, heating of the regulator can be efficiently restrained and energy savings can be realized by reducing useless energy consumption.
In another embodiment of the above power supply device, the power supply device is used with a facsimile apparatus having a modem operated by the second DC voltage produced in the second DC voltage producing part, the modem conducting transmission with an external transmission line. In this embodiment of the power supply device, the reducing means reduces a load current necessary for the modem to operate when a copy function is conducted. Thereby, even if the load current loaded to the first DC voltage producing part increases due to execution of the copy function, the load current necessary for the modem to operate can be reduced by the reducing means.
Accordingly, the load current loaded to the second DC voltage producing part can be reduced and the DC voltage value loaded to the regulator can be reduced. As a result, the amount of energy emitted from the regulator can be certainly reduced.
In a further embodiment of the power supply device, the power supply device is applied to a facsimile apparatus that has a setting part for setting an operating condition of the reducing means. In this embodiment of the power supply device, the reducing operation of the reducing means is selectively conducted based on the operating condition set by the setting part when a call signal from the external transmission line is detected while the copy function is conducted.
In the above application of the power supply device, the reducing operation of the load current for modem operation by the reducing means can be selectively conducted based on the operating condition set by the setting part when the call signal from the external transmission line is detected while the copy function is conducted. Thereby, even if the transmission with the external transmission line becomes impossible due to the copy function and the load current for modem operation being reduced by the reducing means, the second DC voltage can be supplied to the modem based on the operating condition set by the setting part. Therefore, transmission with the external transmission line can be performed while the copy function is conducted.